Can mass balance be trusted in estimating N loss for meat-poultry housing?

Quantification of ammonia loss from animal feeding operations by measuring gaseous concentration and air exchange through the emitting source is not always practical, e.g., under natural ventilation conditions. Mass balance over an extended period of time may offer possibilities of remedy. This study compares two NH₃-N emission estimate approaches for a commercial turkey grow-out house over one year period: a) a concentration-flow-integration (CFI) method (considered as the reference method), and b) a nitrogen (N) mass-balance method. The CFI NH₃-N emission was determined by continuously measuring the NH₃ concentration and exhaust air flow rate through the turkey house with a state-of-the-art mobile air emission unit. The mass-balance N emission was calculated by balancing the total N inputs (new bedding, young birds, feed) and N output (litter cake removed between flocks, litter removed at cleanout, amount of marketed birds, mortality, and body N content). The production-related data were acquired from the records kept or presented to the cooperative producer. The results revealed unexpectedly large discrepancy in NH₃-N loss between the two methods. The outcome of this study cast serious doubt about the adequacy of using mass balance for estimating NH ₃ emissions from a dynamic production system such as turkey houses.